Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Fri, 4 Feb 2022 12:10:13 +0100
From:   Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To:     "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc:     Andy Lutomirski <luto@amacapital.net>,
        Boqun Feng <boqun.feng@gmail.com>,
        Will Deacon <will@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Waiman Long <longman@redhat.com>,
        Sultan Alsawaf <sultan@kerneltoast.com>,
        Theodore Ts'o <tytso@mit.edu>,
        Andy Lutomirski <luto@kernel.org>,
        Jonathan =?utf-8?Q?Neusch=C3=A4fer?= <j.neuschaefer@gmx.net>,
        LKML <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH v2] random: remove batched entropy locking
Message-ID: <Yf0JlXf3ARsBpL9K@linutronix.de>
References: <CAHmME9pe2BEJV4WiZNHmDmH_XK621Qqr1JCBdgTNZmr4JGBA4w@mail.gmail.com>
 <20220128223548.97807-1-Jason@zx2c4.com>
 <CAHmME9qtjZX2kVNSQqUsTrZv1cdR8y6n3yZS-RnpVCCzX9okcA@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable
In-Reply-To: <CAHmME9qtjZX2kVNSQqUsTrZv1cdR8y6n3yZS-RnpVCCzX9okcA@mail.gmail.com>
Precedence: bulk

On 2022-02-04 01:27:55 [+0100], Jason A. Donenfeld wrote:
> Hey Andy,
>=20
> Think I could bug you to review this patch? The general idea is based
> on your original patch, and I think this fits what we talked about on
> IRC. I figure we'll probably both page this out of our minds after
> another week or two of not thinking about it.
>=20
> It's here on cgit if that's easier to look at:
> https://git.kernel.org/pub/scm/linux/kernel/git/crng/random.git/commit/?h=
=3Djd/no-batch-lock

Please don't merge this:
- This splat only occurs with CONFIG_PROVE_RAW_LOCK_NESTING enabled.
  This option has this in its description:
  =E2=94=82 NOTE: There are known nesting problems. So if you enable this
  =E2=94=82 option expect lockdep splats until these problems have been ful=
ly
  =E2=94=82 addressed which is work in progress. This config switch allows =
to
  =E2=94=82 identify and analyze these problems. It will be removed and the
  =E2=94=82 check permanently enabled once the main issues have been fixed.

- The problem identified by the splat affects only PREEMPT_RT. Non-RT is
  not affected by this.

- This patch disables interrupts and invokes extract_crng() which leads
  to other problems.


If this patch is the way then it should be merged together with the
other outstanding issues.

> Thanks,
> Jason

Sebastian